Most human infants produce ample quantities of lactase for milk digestion. However, in the vast majority of adult humans, the
gene which specifies production of lactase is turned "off" and these individuals cannot digest lactose - they are lactose
intolerant.

Receptors on our tongues bind to chemicals in our food and relay the information about the chemicals to our brain.
Surprisingly, all those wonderful tastes are transmitted to our brains through only four types of receptors on our tongues -
those for sweet, sour, salt and bitter.